The invention relates to an electron beam generator for an electron beam gun, having a cathode, a control electrode and an anode which are disposed in an evacuable acceleration chamber.
Electron beam generators of the stated kind are used in metallurgy. They generate an electron beam which, being focused by an electromagnetic focusing system, is directed against a workpiece for the purpose, for example, of removing material therefrom, or of melting it. The need in this case arises for adapting its power to various working procedures and materials, for example by varying the accelerating voltage and the beam current. It has been found, however, that the known electron beam generators can be operated in an optimum manner only within a narrow range of power. This optimum power range is defined by the emittance--the product of the focus radius times the solid angle--which varies with the beam current. To make optimum use of the entire working range of an electron beam gun it has therefore been necessary to replace the gun from one case to the next.